public class Test {
    public static void main(String[] args) {
        String s1=String.valueOf(123);//把整数123转化成字符串s1
        System.out.println(s1);
        int ret=Integer.valueOf("123");//把字符串"123"转化成整数123
        System.out.println(ret+10);
        int m=Integer.parseInt("123");
        System.out.println(m+20);
    }
}
